The present invention relates to functionalized polymers. More particularly, it concerns a method of preparation of functionalized polymers which impart improved properties to lubricating oil compositions.
Lubricating compositions ordinarily are formulated with various additives to enhance their performance. Some additives have low solubility in oil or their solubility may decrease when combined with other additives. Additives that have poor oil solubility are incorporated into lubricating oil compositions with the aid of dispersants, viscosity index improvers, or pour point dispersants.
Prior art dispersants include copolymers of acrylic ester and dicarboxylic acid functionalized with a Mannich base and a primary or secondary amine as described in U.S. Pat. No. 4,668,412.
Polymers functionalized with an amine alone by prior art methods often yield dark colored products. When incorporated into lubricating oil, the amine-functionalized polymers cause turbidity and formation of a precipitate. These undesirable effects are caused by residual amine remaining in the product.
Surprisingly, it has been discovered that polymers can be functionalized with an amine in the absence of a Mannich base to yield light colored products that are oil-soluble and have good dispersability, oxidation stability and viscosity improving properties.